Energy-Saving Processesfor Increasing the MolecularWeight via a Falling Film Reactor in Large-ScaleProduction of PET Fiber

The industrial production of poly­(ethylene terephthalate) (PET) melt in these decades has relied on a high-energy-consuming horizontal stirring reactor, especially for industrial-grade PET where the process involves interrupting the melt reaction and a lengthy solid-state polycondensation procedure. A falling film melt polycondensation reactor model was established and used to simulate the production process of industrial-grade PET, and the process was verified in production. On this basis, two new process designs were implemented to produce both clothing-grade and industrial-grade PET. Due to the efficient mass transfer of the falling film reactor, properties such as the molecular weight and terminal carboxyl content of products were improved, along with an increase in production efficiency. The clothing-grade PET production with a falling film reactor reduced electricity consumption by 10–20%. When dual falling film reactors in series replaced the solid-state polycondensation process, the energy and water consumption dropped to surprisingly low levels owing to the elimination of several production stages.